Unless I'm missing something different about GMT800's then a shackle isn't going to help you, other than going from a drop shackle to a stock one. The shorter the shackle, the higher the truck body rides in relation to the axle (lift) - but the stock shackle is very short already, so it would be near impossible for them to make a shackle shorter than that in order to gain more lift.

Richard

 

Perhaps he could go old school and do a shackle reverse/shackle flip like when the 4x4 guys want to lift there trucks they used to swap the rear shackles from side to side and flip them upside down and they would get like 4” lift and proper driveline geometry

The link is to give an image representation



https://www.google.com/search?q=shac...WHTuRAYJiEF4M:

 

Is there a way to find out about the crew cab. There 4 inch drop is a flip kit with the shackle flip. Would those fir a ext cab .

 

I did some digging and just everyone is curious. The crew cab is the same part number through djm. Same with 07-13 .it's all the same parts. So you can order a flip kit 4 inch with a shackle hanger for a crew cab and bolt it to our 99-02 trucks.